A measuring instrument of the type disclosed herein can be used for simultaneously measuring two different types of energy or power, such as active energy, reactive energy and apparent energy or active power, reactive power, and apparent power. In addition, different combinations of these quantities can be measured. The measuring instrument can be an electrical meter including a pulse width modulator which can measure active energy and reactive energy simultaneously. It is not necessary for the reactive energy to be measured directly. It can be measured indirectly, for example, in a conventional Q-meter in which a Q-value is measured and is related mathematically to the measured active energy to obtain the reactive energy value.
A circuit arrangement of the type mentioned above is commercially available, and has been described at least obliquely in the periodical "Landis & Gyr - Mitteilungen", 32nd year (1985), 1, "Tariff Calculators TARIGYR 400," at pages 4 to 8.